Qt: Make fullscreen open on same display as main window

src/duckstation-qt/mainwindow.cpp

@@ -387,7 +387,12 @@ void MainWindow::createDisplayWidget(bool fullscreen, bool render_to_main, bool
     // Don't risk doing this on Wayland, it really doesn't like window state changes,
     // and positioning has no effect anyway.
     if (!s_use_central_widget)
-      restoreDisplayWindowGeometryFromConfig();
+    {
+      if (isVisible())
+        container->move(pos());
+      else
+        restoreDisplayWindowGeometryFromConfig();
+    }
 
     if (!is_exclusive_fullscreen)
       container->showFullScreen();